Are they worth the investment, and if so what steering stem and stabilizer do you guys reccomend and what is the ball park to pay for them ?

I would be using it on a YFZ 450 and I am racing a GP Series

 

I have a chromed Lonestar Anti-vibe steering stem that is great. It takes a noticeable amount of vibe out when racing. I also bought a steering stabilizer but later took it off. I didn't like how it stiffened up the steering.